Leaks in the duct work are amongst the largest energy wasters inmost homes, both site built and mobile homes. Leaks are more prevalent in most homes over 10 years old. Leaks in the return duct work pressurize the home and raises the supply temperature. It also introduces higher humidity into the system cutting energy efficiency ratings (EER) by as much as 50 percent. Supply system leaks will send conditioned air outside through the infiltration routes and depressurize the home. These pressure differences extend the HVAC unit’s running time causing an average 22 percent increase in energy usage. New methods of sealing the duct connections with masking material are not expensive and will greatly reduce leakage and higher energy use.